Genetics · Question of the Day

Genetics Question of the Day

A fresh daily question to build accuracy, reinforce recall, and turn practice into a steady habit.

Thursday, September 17, 2026

A large mainland population of butterflies with an allele frequency of $p=0.8$ for a wing-spot gene colonizes a new island. The founding group consists of 20 individuals from the mainland. Concurrently, 30 butterflies from a different island population, where the same allele has a frequency of $p=0.3$ , also arrive. Assuming these 50 butterflies form a single, randomly mating new population, what is the initial allele frequency for $p$ on the island?

Keep practicing Genetics

Question of the Day

Answer today's Genetics question, reveal the full explanation, then keep the streak going with a new question every day.

0.50 (correct answer)
0.55
0.60
0.80

Explanation: The allele frequency in an admixed population is the weighted average of the frequencies from the source populations, weighted by their proportional contribution to the new population.\n1. Source population 1: $N_1 = 20$ , $p_1 = 0.8$ .\n2. Source population 2: $N_2 = 30$ , $p_2 = 0.3$ .\n3. Total size of the new population: $N_{total} = N_1 + N_2 = 20 + 30 = 50$ .\n4. The new allele frequency $p_{new}$ is calculated as: $p_{new} = \frac{(N_1 \times p_1) + (N_2 \times p_2)}{N_{total}} = \frac{(20 \times 0.8) + (30 \times 0.3)}{50} = \frac{16 + 9}{50} = \frac{25}{50} = 0.50$ .\n\nDistractor B is the unweighted, simple average of the two frequencies $(0.8 + 0.3)/2 = 0.55$ . Distractor C is an incorrect calculation. Distractor D is the allele frequency of the larger source population, ignoring the contribution of the smaller one.